I operate as a freelance HR consultant. I have a few associate relationships with HR companies that engage my services on behalf of their clients.
One such company I have been with for a few months. They have only just this week sent me their Associate Agreement for me to sign: however I am not happy with the terms.
Question 1 is, am I “governed” by the agreement even though I have only just been given it and NOT signed it, or can I walk away (I am self employed and they invoice me as a supplier).

Question 2: the same company has “amended” an invoice I have submitted and paid me less that was on the invoice. Their argument being that they wanted to amend it to come into line with the Agreement (but I have only just been given that!).
Aside from being bad business, can they just pay what they want?

Many thanks!